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Biological Profiles

Caranx hippos was first described by Linnaeus in 1766 as Scomber hippos. It was first referred
to as Caranx hippos in 1766 and this name is still in use. Through the years, it has appeared under a
variety of different names. Caranx is derived from the French word "carangue" which means a Caribbean
fish while hippos is Greek for "horse". Although these names are no longer valid, these included
Scomber carangus Bloch 1793, Caranx carangus Bloch 1793, Caranx carangua Lacepede 1801,
Caranx erythrurus Lacepede 1801, Caranx antilliarum Bennett 1840, Caranx defensor DeKay
1842, Trachurus cordyla Gronow 1854, Caranx esculentus Girard 1859, Caranx hippos caninus
Gunther 1869, and Caranx hippos tropicus Nichols 1920.

The crevalle jack's range consists mainly of the coastal areas of the western Atlantic Ocean from Novia Scotia to
Uruguay. They also often are found throughout the Gulf of Mexico, especially along the coast of Texas and the west
coast of Florida.

World distribution map for the crevalle jack

Habitat

The crevalle jack is found in oceanic, estuarine or riverine environments. This is influenced by the life stage
of the fish. They primarily are found along the continental shelf, but occur in waters as deep as 327 feet
(100 m). Fish found in these deep waters are usually larger individuals. Larval and juvenile jack crevalles are
found in upstream currents and are common in shallow brackish waters. Adults, on the other hand, usually occupy
upstream currents, reefs, offshore areas or shallow inshore areas. Jack crevalles live in a variety of temperatures
and salinities. Adults usually inhabit areas with temperatures between 64-92.5°F (18-33.6ēC) of water and larvae
are found in areas with temperatures between 69-84.9°F (20.4-29.4ēC) of water. Crevalle jacks have been found in
fresh water to salt water environments, depending on life stage. Larvae have been collected in areas with
salinities between 35.2-36.7 parts per thousand (ppt). Adults have been found in freshwater habitats as well
as those with a salinity of 43.8 ppt. They are most commonly found at salinity above 30 ppt. The crevalle jack
is a pelagic fish. Both adults and juveniles are usually found in schools. However, larger individuals may be
found swimming the waters alone.

The crevalle jack has a body depth of about three times its fork length. It has large eyes. The chest is scaleless
except for a small patch of scales in front of the pelvic fins. This patch is apparent by the time the fish
reaches a fork length of 0.98 inches (2.5 cm). The crevalle jack is the only jack in the western Atlantic Ocean
with this patch of scales. There is an oval black spot on the pectoral fins; this appears at about 4.72 inches
(12.0 cm). Between the seventh and the eighth spines of the adult there is an overgrowth of skin. The two most
distinguishable features of this fish are the patch of scales between the pelvic fins and the oval, black spot
on the pectoral fins.

The crevalle jack is greenish-bluish or bluish-black above and silvery white to yellowish or golden below.
This serves to blend in with the water from a predator searching from above, and to blend with the sunlight
from a predator hunting from below. There is an oval, black spot on the pectoral fins. Juveniles have 5 dark
bars on their bodies. These black bars are present until the fish reaches a size of 6.46 inches (16.4 cm).
There is an area of dark pigment above the peduncle that appears at 1.18 in. (3.0 cm) and is very dark once
the fish reaches a size greater that 3.94 inches (10.0 cm) in length.

The juvenile has pigment spots on
the anal spines and membranes, which disappear by the time its size reaches 1.38 inches (3.5 cm). The pelvic
fin remains unpigmented after 0.79 inches (20 mm) and at about 1.18 inches (3.0 cm) the pigment of the caudal
fins develops. The coloration of the juvenile holds between 0.79-1.57 inches (2.0-4.0 cm) and fades between
1.57-1.97 inches (4.0-5.0 cm).

The crevalle jack has three paired patches of small villiform teeth located dorsally. These teeth are larger
than the premaxillary teeth. Ventrally, the jack crevalle has a single pair of triangular patches of smaller
teeth. These teeth, in combination with the air bladder, are responsible for the croaking noise it makes when
it is caught. The fish rasp their upper and lower teeth together, this combined with air bladder resonance,
are the factors contributing to the sound.

ˇSize, Age, and Growth

The maximum size of a crevalle jack is 39.8 inches (101 cm) and 55.1 pounds (25 kg), however they are common to 23.6
inches (60 cm). After the juvenile reaches a size of 1.97 inches (5.0 cm), its growth rate increases. Females are
typically larger than males.

The crevalle jack is a diurnal predator. Adults prey upon on a variety of fish, shrimp and invertebrates.
Juveniles feed mainly on small fish and crustaceans.

ˇ Reproduction

The spawning season of the crevalle jack is early March to early September. Spawning occurs offshore in the
southeastern Atlantic coast and in the Gulf Stream, including any associated currents. The crevalle jack has
been found to spawn in both tropical and subtropical environments. The eggs of the crevalle jack are between
.03-.04 inches (0.7-0.9 mm) in diameter and the newly hatched larvae are between 0.06-0.07 inches (1.6-1.8 mm)
in length. The larva use estuaries as nurseries. In juveniles the small patch scales on the chest form at 0.98
inches (25 mm). The pigmentation of the first dorsal fin decreases above 1.2 inches (30 mm), pigment appears on
the second dorsal fin at 1.2 inches (30 mm), and the pelvic fin is unpigmented above 0.8 inches (20 mm). The
pectoral spot develops at about 4.7 inches (120 mm).

The crevalle jack is prey for many surface feeding carnivores, such as finfish including the striped marlin
(Tetrapturus audax), and sea birds.

ˇ Parasites

Two known parasites of the crevalle jack are Stephanostomum ditrematis and Bucephalus varicus,
both digenic trematodes. S. ditrematis inhabits the rectum of the host. It is common in
fish taken off the coasts of Massachusetts and Florida. This parasite affects all carangids.
Another known parasite, B. varicus, inhabits the pyloric junction or the entire length of
the intestine. Copepods are also common parasites to the crevalle jack including Anuretes heckelii
found on the wall of branchial cavities, Caligus chorinemi and Caligus coryphaenae are both
parasitic on the body surface as well as in the branchial cavities, and Lernaeenicus longiventris
which is parasitic in the flesh of the fish. Other parasites include protozoans, monogenea (gillworms),
cestoda (tapeworms), and nematoda (roundworms).

Importance to Humans

Although the crevalle jack is a relevantly unimportant commercial fish, it is fished commercially throughout the
year in southwest Florida, and in the spring, fall, and summer in the Gulf of Mexico. It is an important sport fish,
and is exploited throughout its range. It is the most common large jack caught off the west coast of Florida.

There have been some reports of ciguatera poisoning associated with this jack. Ciguatera poisoning occurs when
humans eat a fish that has eaten a toxin that is produced by the dinoflagellate, Gambierdiscus toxicus,
and it is digested by the fish. This poisoning, although it is usually self-limiting, can affect humans in many
ways. It has gastrointestinal, neurological, and cardiovascular symptoms.

Crevalle jackscourtesy Virginia Institute of Marine Science

Conservation

The crevalle jack is not listed as endangered or vulnerable with the World Conservation Union (IUCN). The IUCN is a
global union of states, governmental agencies, and non-governmental organizations in a partnership
that assesses the conservation status of species.